Senator Rod Zimmer’s marriage to 23-year-old Maygan Sensenberger was barely a year old, and in the skies over Saskatchewan, it already seemed to be coming apart. After the 69-year-old former businessman started experiencing breathing problems, Ms. Sensenberger allegedly swore at other passengers, threatened to slit his throat and “take the plane down.”

The couple had been enroute to Mr. Zimmer’s brother’s farm to celebrate their first anniversary. Instead, they spent the occasion separated by court order in Saskatoon.

For critics, it was a predictable fallout for Mr. Zimmer’s foray into intergenerational romance.

And yet, for every Zimmer and Sensenberger, there are plenty of Charlie and Oona Chaplins. At 54, the ageing silent film star took up with the 18-year-old daughter of playwright Eugene O’Neill. The pair stayed happily married for 35 years until Chaplin’s death in 1977.

Middle-aged newspaper baron William Randolph Hearst’s extra-marital dalliances with a teenaged actress are forever immortalized in Citizen Kane. What the film omits is that Hearst remained faithful to his young mistress for a full 34 years until his death in 1951.

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But while it has been an institution since ancient times, the intergenerational marriage nevertheless continues to fascinate and irk. Known as the May-December romance, it seems to symbolize everything society fears is true of marriage: Partnerships of convenience driven by money, sex and power. But when age-gapped couples can boast low divorce rates and the occasion silver anniversary, could the arrangement be more compatible than we fear?

“Overall, regardless of age, all relationships are the same,” said Tom Caplan, a Montreal-based marriage and family therapist. “If you’re really good friends, you support your partner under any circumstances.”

In popular media, May-December pairings are such a common trope that they are barely noticed. In Sean Connery’s last appearance as James Bond, he acted alongside women who had been in diapers the first time agent 007 appeared onscreen.

The trope is remarkably common among Canadian political leaders. Pierre Trudeau, 52, married Margaret Sinclair, 22. Joe Clark was 34 when he married staffer Maureen McTeer, 21. Brian Mulroney was 34 when he married Mila Pivnicki, 19.

In 1983, Erik Nielsen, Mr. Mulroney’s widower deputy prime minister, announced his sudden marriage to Shelley Coxford, a House of Commons security guard who appeared to be about 30 years his junior. “We decided not to make my age public,” she told the press at the time. Twenty-five years later, Shelley was at Mr. Nielsen’s side when he died of a heart attack in Kelowna.

Kim Campbell, Canada’s 19th Prime Minister, has seen the May-December relationship from both sides. At 22, she entered into an 11-year marriage with Nathan Divinsky, a UBC mathematics professor and chess grand champion then in his mid-40s.

Now, at 65, Ms. Campbell lives in Paris with Hershey Felder, a 44-year-old Montreal-born playwright and composer. “The natural reaction from people is, ‘Oh, Hershey wants a mother,’” Ms. Campbell told Postmedia in 2008. “But of all the men I’ve ever known he’s the one who least wanted a mother.”

In the marriages of the developed world, there is – and always has been – a built-in age disparity. In both Canada and the United States, the average groom is two to three years older than his bride. In at least 40% of married Canadians, the gap is even wider, with both partners born at least four years apart.

Furthermore, couples with “extremely large” age gaps also had one of the country’s lowest divorce rates, according to 1994 Statistics Canada data. The same data also shows that the average age-discrepant couple is actually poorer than their same-age equivalents.

Vikki Stark, director of the Montreal-based Sedona Counselling Centre, says the arrangement, while rare, is an understandable tradeoff.

For men, the arrangement “demonstrates to the world that he’s still virile and masculine,” said Ms. Stark. “From the woman’s point of view, she has security and the potential of living an extraordinary life … he’s a means to an end.”

Any marriage is a morass of sex and power dynamics, it is just more obvious in May-December relationship. “But who says that they’re not laughing and having a good time and sharing a bowl of popcorn?” said Ms. Stark.

In 2007, a Stanford researcher even theorized that ancient May-December relationships may be why humans have become one of the planet’s longest-living mammals. Demographer Cedric Puleston compared South American hunter gatherer societies against modern Canadians and concluded that when old men father children, their descendants live longer.

As women occupy leadership positions and fetch higher salaries, they are increasingly adopting the elder role in May-December romances. In 2003, British statisticians discovered that, from 1963 to 1998, the rate of women taking younger husbands had jumped by nearly two thirds.

Which is not to say the intergenerational marriage is not rife with obstacles. In the infatuation of a new relationship, “people are not clear thinking,” said Sig Taylor, a Calgary couples and marriage counselor. “They’re not thinking about the age gap, they’re not thinking about the differences in energy [and] once their hormones come back to balance, they’re faced with the realities,” he said.

Age-gapped couples find themselves living in “different eras,” notes David McKenzie, a Vancouver-area couples and sex therapist. He noted his own grandfather took an 18-year-old bride at the age of 36.

As for children, “if [women] are 30 and he’s 55, they have to realize that he’s got a limited shelf life,” said Mr. McKenzie.

The arrangement can apparently suck the life out of young brides. After analyzing the demographic data for nearly two million Danish couples, in 2010 German researcher Sven Drefahl concluded that women with older husbands die sooner.

And while a new couple basks in the glow of young love, the partnership can have untold ripples on children and ex-wives who fear being written out of the will and friends who question the couple’s mental state.

“It’s a pressure cooker relationship,” said Ms. Stark. “There’s so much pressure from the outside, even if they’re happy in their living room.”

Eugene O’Neill disowned his daughter for marrying Chaplin, and most of Mr. Zimmer’s family was absent from his 2011 wedding to Ms. Sensenberger.

Woody Allen’s career and reputation has largely recovered from the early-1990s revelations that he was having an affair with his wife’s 21-year-old adopted stepdaughter, Soon Yi Previn.

Twenty years later, the now-30 Previn can still be seen at Mr. Allen’s side at red carpet events and galas. “What was the scandal? I fell in love with this girl, married her. We have been married for almost 15 years now,” Mr. Allen told Reuters in 2011.

Among the family Mr. Allen left behind, however, the bitterness remains — but not necessarily because of the age difference.

In June of this year, the director’s estranged son, Rhodes scholar Ronan Farrow, wrote on his Twitter feed, “‘Happy father’s day – or as they call it in my family, happy brother-in-law’s day.”